POLY(VINYLPYRIDINE) AND RELATED POLYMERS AS GUESTS FOR ORGANOTRANSITION-METAL-BASED NLO CHROMOPHORES

We have investigated a set of three polymers functionalized by tungste n pentacarbonyl as a chromophore for second harmonic generation(SHG). Films were poled by the Corona poling method, and their second-order n onlinear responses were measured via in situ SHG while poling. It is f ound that poly(vinylpyridine) can be used as a probe to obtain the sig n of the hyperpolarizability coefficient of the chromophores beta. The se polymers all exhibit modest SHG properties. This raises several int eresting theoretical and practical questions which are discussed: ther mal stability, effect of a negative sign of beta, importance of the ch romophore dipole moment, and poling efficiency of chromophores based o n tungsten pentacarbonyl. Relaxation mechanisms are also discussed in relation to the structure of the polymers backbone.